If these are full span strip ailerons then don't worry about it. The stock you remove will be just fine. If they are barn door types then perhaps make them a rib bay or two longer.

In any even extending them back by 1/4 inch wouldn't create any noticable difference other than to ensure a slightly snappier aileron response.

While you're at it you may want to incorporate some differential in the linkage so the up throw is more than the down throw for less adverse yaw on such a slow flying model.